Introduce search_kwargs for Custom Parameters in BingSearchAPIWrapper (#13525)

Added a `search_kwargs` field to BingSearchAPIWrapper in
`bing_search.py,` enabling users to include extra keyword arguments in
Bing search queries. This update, like specifying language preferences,
adds more customization to searches. The `search_kwargs` seamlessly
merge with standard parameters in `_bing_search_results` method.

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/langchain/langchain/utilities/bing_search.py

@@ -7,7 +7,7 @@ from typing import Dict, List
 
 import requests
 
-from langchain.pydantic_v1 import BaseModel, Extra, root_validator
+from langchain.pydantic_v1 import BaseModel, Extra, Field, root_validator
 from langchain.utils import get_from_dict_or_env
 
 
@@ -21,6 +21,8 @@ class BingSearchAPIWrapper(BaseModel):
     bing_subscription_key: str
     bing_search_url: str
     k: int = 10
+    search_kwargs: dict = Field(default_factory=dict)
+    """Additional keyword arguments to pass to the search request."""
 
     class Config:
         """Configuration for this pydantic object."""
@@ -34,6 +36,7 @@ class BingSearchAPIWrapper(BaseModel):
             "count": count,
             "textDecorations": True,
             "textFormat": "HTML",
+            **self.search_kwargs,
         }
         response = requests.get(
             self.bing_search_url,